ICC色彩管理官方演示文档 - 色彩管理网.ppt

4d Interpolation table Copyright 2003 International Color Consortium 32 Shaper/MFT Processing: e.g. CMYK input profile C M Y 4d Interpolation table X L* Y or a* Z b* K Device to PCS AToBnTag (n=0, 1, 2 depending upon the rendering intent specified) ? Non-invertible profile for converting CMYK data to PCS Four Rendering Intents ? Relative colorimetric – the white point of the actual medium is mapped to the white point of the reference illuminant (i.e. L*a*b* = 100, 0, 0 for the medium). The colours map accordingly. ? Absolute colorimetric – the white-point of the illuminant maps to the white point of the reference illuminant (i.e. L*a*b* = 100, 0, 0 for D50). The colours map accordingly. ? 33 Note: Both may allow for chromatic adaptation. Copyright 2003 International Color Consortium Copyright 2003 International Color Consortium 34 Four Rendering Intents ? Perceptual – the full gamut of the image is compressed or expanded to fill the gamut of the destination device. Grey balance is usually preserved, but colorimetric accuracy might not be. ? Saturation – the saturation of the pixels in the image is preserved, perhaps at the expense of accuracy in hue and lightness. Copyright 2003 International Color Consortium 35 The PCS ? In the ICC workflow, the standard colour space is called the profile connection space (PCS). ? Each profile describes the transformation from source (device) space to PCS, and vice versa in case of output profiles. ? The PCS is based on a D50 illumination environment, but comes in two forms – one for the colorimetric renderings and one for the perceptual and saturation renderings. Copyright 2003 International Color Consortium 36 PCS definitions ? Colorimetric renderings define black as L*a*b* = 0,0,0. White (100, 0, 0) is either the perfect diffuser (absolute) or the medium (relative). ? While the PCS is defined using D50 for all render